Add debuggable=true to AppRTCMobile manifest.
Add debuggable=true to AppRTCMobile manifest.

Improves possibility to debug the demo application using adb.
As an example, now allows 'adb run as' which is useful when profiling CPU. It enables us to do profiling on non-rooted devices (excluding details).

BUG=NONE

Review-Url: https://codereview.webrtc.org/2676983003
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#16446}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 447dba958681dc3054c3fd92ef571176ab52c279

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